A classmate of suspected gunman Nikolas Cruz, who allegedly went on a shooting spree Wednesday killing at least 17 at Marjory Stoneman Douglas High School in South Florida, claims that Cruz threatened last year to "shoot up" the school.

"About a year ago I saw him upset in the morning," student Brent Black told ABC News. "And I was like, 'yo what's wrong with you?' And he was like 'umm, don't know.' And I was like 'what's up with you?' He's like 'I swear to God I'll shoot up this school.' And then I was like 'watch what you're saying around me,' and then I just left him after that. He came up to me later on the day and apologized for what he said."

Meanwhile, another student told WJXT that his classmates had "joked" that Cruz would indeed one day unleash a reign of terror and bullets upon Marjory Stoneman Douglas High School.

"Honestly, a lot of people were saying it was going to be him," the student, who did not provide his name, told WJXT. "A lot of kids joked around like that, saying he would be the one to shoot up the school. But it turns out everyone predicted it. That's it."

The student also said that Cruz would have known the layout of the Parkland, Florida, school and its schedule. "He was on the third floor," the student said. "He knows the school layout. He knows where everyone would be at right now. He's been in fire drills. He's prepared for this stuff."

And a math teacher at the school Jim Gard, told ABC News he believes Cruz had been banned from bringing a backpack to school when he was a student there.